Impact mechanism for a repeatedly striking hand-held machine tool

Abstract

A percussion mechanism for a repetitively hammering hand power tool, whose striking frequency and striking intensity are controllable independently of one another, has a striker ( 2 ), movable axially forward and backward in a guide barrel ( 1 ), and a device ( 5 ) exerting pressure on the striker ( 2 ), as a result of which the striker can be set into a forward motion in the direction of a tool bit ( 4 ) that is insertable into the hand power tool. A blocking element ( 10 ) is also provided, with which the striker ( 2 ) is blockable in its forward motion, and the striking frequency of the striker ( 2 ) is adjustable by controlling the blocking time of the blocking element ( 10 ).

1. A percussion mechanism for a repetitively hammering hand power tool in the form of a rotary hammer, the percussion mechanism having a striker ( 2 ), movable axially forward and backward in a guide barrel ( 1 ) and imparting impacts directly to an end section of a tool bit ( 4 ) that is insertable into the hand power tool, having a device ( 5 ) that exerts pressure on the striker ( 2 ), by which the striker ( 2 ) is capable of being set into a forward motion in the direction of the tool bit ( 4 ), wherein a blocking element ( 10 ) is provided, with which the striker ( 2 ) is blockable in its forward motion; and wherein the striking frequency of the striker ( 2 ) is adjustable by controlling the blocking time of the blocking element ( 10 ), so that the striking frequency of the striker ( 2 ) depends on how long the blocking element ( 10 ) blocks the forward motion of the striker ( 2 ), wherein the device exerting pressure on the striker ( 2 ) comprises a pressure reservoir ( 5 ) that is fillable with a gas and that is located on the side of the striker ( 2 ) diametrically opposite the tool bit ( 4 ), and wherein the blocking time of the blocking element ( 10 ) is controllable as a function of a pressure level in the pressure reservoir ( 5 ). 
   
   
     2. The percussion mechanism in accordance with  claim 1 , wherein the gas in the form of air is deliverable to the pressure reservoir ( 5 ) via an inlet valve ( 6 ). 
   
   
     3. The percussion mechanism in accordance with  claim 2 , wherein the quantity of the delivered gas and thus the pressure exerted on the striker ( 2 ) are controllable. 
   
   
     4. The percussion mechanism in accordance  claim 2 , wherein a pump device ( 7 ) is provided, which delivers the gas to the pressure reservoir ( 5 ). 
   
   
     5. The percussion mechanism in accordance with  claim 4 , wherein the pump device ( 7 ) is located in the hand power tool. 
   
   
     6. The percussion mechanism in accordance with  claim 1 , wherein the pressure reservoir ( 5 ) has an outlet valve ( 8 ), which limits the gas pressure to a predeterminable maximum value. 
   
   
     7. The percussion mechanism in accordance with  claim 1 , wherein the blocking time of the blocking element ( 10 ) is controllable as a function of a fixedly predetermined or user-selectable striking frequency. 
   
   
     8. The percussion mechanism in accordance with  claim 1 , further having a control unit ( 17 ) configured for adjusting the striking frequency of the striker ( 2 ) by controlling the blocking time of the blocking element ( 10 ), so that the striking frequency of the striker ( 2 ) depends on how long the blocking element ( 10 ) blocks the forward motion of the striker ( 2 ). 
   
   
     9. The percussion mechanism in accordance with  claim 8 , wherein the control unit ( 17 ) includes an electronically drivable actuator which actuates the blocking element ( 10 ). 
   
   
     10. The percussion mechanism as defined in  claim 8 , wherein said control unit ( 17 ) includes an electrically drivable actuator which comprises an electromagnet. 
   
   
     11. The percussion mechanism as defined in  claim 8 , wherein sensors ( 18 ,  19 ,  20 ) are provided, said control unit being configured to process data from at least two input channels individually connected to different ones of said sensors ( 18 ,  19 ,  20 ) for controlling the blocking time of the blocking element ( 10 ). 
   
   
     12. The percussion mechanism in accordance with  claim 1 , wherein the percussion mechanism comprises a mechanical or electrical acting device, by which the striker ( 2 ) is set into a rearward motion away from the tool bit ( 4 ). 
   
   
     13. The percussion mechanism as defined in  claim 12 , wherein the mechanical or electrical acting device is configured as a compression spring ( 13 ). 
   
   
     14. The percussion mechanism as defined in  claim 13 , wherein the compression spring ( 13 ) is located in front of said striker ( 2 ) in the direction towards said tool bit ( 4 ).